July 2017

Out on a limb: Back to the evidence

The farther you go up the kinetic chain, the more some things about evidence-based medicine stay the same.

The spine differs in many ways from most of the lower extrem­ity segments of the kinetic chain. Obvious differences include the shape and function of the bony structures, the complex roles of the adjacent muscles, and how the spine responds to the demands of movement.

However, the spine literature can be just as complex and frustrating as the lower extremity literature for clinicians looking for solid evidence on which to base treatment. This theme is repeated throughout the special section in this issue on how lower extremity care can help improve spinal health (see “Up the Chain,” page 25).

It probably won’t surprise any LER readers to learn that research on the use of foot orthoses in patients with low back pain suffers from many of the same limitations as studies of similar devices for treating knee or hip pain (see “Gaps remain in literature on insoles and back pain,” page 27). These limitations include absent or inadequate sham controls, insufficient attention to dynamic as well as static foot function, and heterogeneous study populations in which significant effects for certain patients can be lost when analysis is based on group means.

Research on how scoliosis bracing affects gait and balance suffers from similar limitations (see “Scoliosis bracing: Potential effects on gait and balance,” page 31)—although the ethics of having scoliotic patients wear sham orthoses make that problem largely unsolvable. But given that the most common diagnosis in this patient population is idiopathic scoliosis—a term that in itself suggests heterogeneity—and that reported rates of inadequate curve correction with bracing vary widely, it’s not a stretch to hypothesize that inconsistencies in the literature may stem at least in part from variability within study populations.

This type of variability may also be an issue when studying the role of the spinal structures in baseball pitching and how lower extremity conditioning can help reduce the risk of low back pain in these athletes (see “A lower body approach to lumbar pain in pitchers,” page 35).

Lower body interventions are being used clinically to manage spinal issues, but it may take time for the literature to catch up.

Current thinking holds that the importance of the spine in the pitching motion primarily involves the transfer of force from the ground to the upper extremities in an effort to maximize ball velocity. That makes sense with regard to the majority of pitchers, for whom the ability to maintain a high velocity is essential.

But knuckleball pitchers—who rely on ball movement rather than velocity to make hitters miss, and typically score well below what more conventional pitchers average on the radar gun—also develop back and neck pain. R.A. Dickey, who currently plays for the Atlanta Braves, and retired knuckleballers Tom Candiotti and Tim Wakefield have all missed significant stretches of playing time with back or neck pain. To me, that suggests factors other than maximizing velocity may be contributing to spinal pain in a subset of pitchers, possibly more than just the knucklers.

Anecdotally, many clinicians are successfully using lower extremity interventions to manage spinal issues, but it seems it may take the literature a while to catch up. Sound familiar?